Call of the Void
by Media Hood Reviews
Summary: SEQUEL TO A SECOND CHANCE! The tale of the Underground brings a small group back to where it began, but there is always more to everything than one may suspect.
1. Chapter 1

**DISCLAIMER:** I do not own Undertale. It is the respective legal property of Toby Fox. Though I do have a copy of the soundtrack on Spotify, so that should count for something.

A.N.: Two different Undertale fanfics in the span of a month or so?! The devil, you say!

Consider this the sequel to my first Undertale story, "A Second Chance". Much like the first, this one is based (albeit much more loosely) on a series of comics by **LynxGriffin**; specifically on "Dogs of Future Past", the tale in which Frisk, Flowey and one of Endogeny's Souls go to the past to save Dr W.D. Gaster. Ideas from the story is present but will have a different approach as to not infringe potential copyright with the author (if that's how that even works, anymore).

Also, rated T due to swearing.

With that out of the way, ON WITH THE SHOW!

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A week has passed after Flowey had come to the Surface. All things considered, even when Alphys seemed… apprehensive regarding the plant, he fit into the groups lifestyle rather seamlessly. While he may not be able to feel love or compassion for any of them, he was still willing to at least try hanging out with them, if only because he could not stand the idea of staying in Frisk's room all day. At least this way, he was exposed to plenty of good shows to watch with the recently engaged Alphys and Undyne (he and the latter got particularly enthusiastic about an Anime involving a bald guy who could beat every enemy in his path with a single punch).

That's not to say that they forgot about the Underground entirely, however, as even after a month and a half, not everything the Monsters had in their possession were taken up to the Surface (Toriel still needed the various books in her collection, for instance). Thus, Asgore had decided to take a small group of Monsters to go Underground and start packing up what was left of the things they needed. Frisk offered to come with them, as there were still some monsters who stayed in the Underground and they wanted to say hello to them. They also brought Flowey with them, because… why not?

Which brings us to now, with the group (consisting of Asgore, Frisk, Flowey, Undyne, Greater Dog, Lesser Dog, Doggo and he, the Great Papyrus [A.N.: and yes, I will always call him that]) just leaving Hotland and walking through the cavern where Undyne and Frisk had their first battle.

"Fuhuhuhuhuhu! Not gonna lie; you gave me a REAL workout that day, Punk! I actually had the chance to work up a sweat for the first time in FOREVER!"

"BUT… WASN'T THAT BECAUSE OF THE HEAT IN HOTLAND?"

"… What are you implying, Papyrus?"

"N-NOTHING, UNDYNE! I, THE GREAT PAPYRUS, AM SIMPLY SAYING THAT SOME OF THAT SWEAT MAY HAVE BEEN FROM A NEAR HEAT-STROKE!"

This actually caused Undyne to stop for a moment and cup her chin in her hand, looking to the side in contemplation. As Greater Dog and Asgore moved on, Frisk, Flowey and Papyrus stayed with Undyne as she thought everything over. Fortunately, they needn't wait for long, as her signature crooked smile came back.

"So you're saying, that Frisk didn't win… because I didn't really lose?"

"W-WELL, IF THAT IS HOW YOU SEE IT."

"Then that means… our fight was simply POSTPONED! Frisk! On the way back from this dump, we are having a full-on REMATCH! No fake hits, no hesitation; we WILL see who is truly the MIGHTIEST FIGHTER BETWEEN US! Fuhuhuhuhuhu! I hope you'll be ready, Punk, cause this time, I won't! Hold! BACK! NGAAAAAAAAAHHHH!"

As Undyne roared with enthusiasm, she found the nearest boulder and suplexed it, if only because she could. During which, Frisk could not contain their laughter and doubled over onto the floor clutching their sides, Flowey sitting next to them with a look of annoyance on his face.

"This is swell, and all, but don't we have more important things to do like, say, GETTING THE CRAP WE CAME FOR AND GETTING THE HELL OUTTA HERE!"

This caused Frisk to finally stop laughing so hard and Undyne to stop suplexing boulders as they stared Flowey inhale and exhale in frustration.

"Y'know, for a little buttercup you sure as hell can scream."

"Trust me, gills; you don't know the half of it."

Around the corner, Asgore popped his head to see the four still standing there.

"Is everything alright, Undyne?"

"No prob, Asgore; just dealing with the leftover heat from Hotland, is all."

"I see… Well, the Dogs and I were just about to reach the River Person, and was I just checking to see if you were still coming."

"WORRY NOT, FORMER KING ASGORE. WE WILL BE WITH YOU MOMENTARILY!"

"Very well; take your time, my friends."

Once Asgore turned back around the corner, Undyne quickly turned to face Flowey, who had now been picked up by Frisk.

"Okay, I gotta ask; what the Hell was up with that screaming earlier, Flowey?"

"Let's just say I'm not entirely fond of being down here again and leave it at that."

"Neither am I, but you don't see ME complaining, do you?"

Flowey seemed to pause for a moment before looking away and speaking softly.

"Look, it doesn't matter, alright? Let's just get the stuff and get this over with. I'm literally missing daylight, down here."

Undyne kept her suspicious eye on the plant for another few seconds before sighing.

"Alright, if you say so pal."

Without another word, the quartet walked off to follow Asgore and the Dogs, with Papyrus looking confused by the interaction between the plant and the former Captain of the Royal Guard, and Frisk's otherwise neutral face somewhat cracking with a look of concern. All was quiet, until:

"HOLY SHIT! We forgot to get Alphys' seaweed-ice cream machine thing!"

"UNDYNE, LANGUAGE! THERE IS A CHILD WITH US!"

"Not important right now, Pap!"

"I'm sure your girlfriend can just make another one."

"FIANCE, you little weed!"

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The four eventually caught up with Asgore and the Dogs, taking the long route through Waterfall and the field of Echo Flowers as they could not find the River Person (Frisk seems to recall them going upstream to Venice and taking a job on a gondola). Thus, they took their time walking through the field to listen to the wishes left behind by the Monsters who had once prayed for the day they could go to the surface. Now, however, they repeat only the cries of joy and triumph of finally having their wish come true after centuries of being trapped. This sense of joy and fulfilment filled Frisk with DETERMINATION.

"Ugh, does EVERYTHING have to fill you with DETERMINATION, Frisk?!"

"I just enjoy the little things in life, Flowey."

"… I think you just made me vomit in my mouth."

"How can you—"

"Don't ask!"

It wasn't long until Frisk and co. walked through the room where Sans had put his prank telescope, which Papyrus had little impulse not to try. This, of course, left the rest of the group trying to hold back their laughter at the sight of a red ring around the skeleton's right eye socket.

"WELL, I'M GLAD TO SEE THAT EVERYONE IS HAVING FUN AS I PIERCE THROUGH THIS LOOKING GLASS, BUT WHAT SEEMS TO BE SO FUNNY?"

Undyne couldn't hold back and started howling with laughter.

"Fuhuhuhuhuhuhuhu! J-just look at your r-reflectiahahahahahahahon!"

Papyrus did so, peering over the side and seeing his visage staring back at him in the water.

"… SAAAAAAAAAAAAAAAAAAANSSSSS!"

_Ba-dum-tis!_

"WHERE DO THOSE CONFOUNDED RIMSHOTS COME FROM?!"

The laughter died down soon after and they continued moving on through Waterfall.

At least, Frisk would've gone with them under normal circumstances. Instead, when they took their first step into the next corridor, everyone, even Flowey, seemed to have suddenly disappeared. Frisk looked around, their face coated in concern and a hint of fear. They could feel a presence looming over them, forcing them to turn to their left to see… the River Person.

"~Tra-la-la~… Beware the man who speaks in hands… You remember that, do you not little one..."

Frisk felt compelled to nod.

"Well… It would seem that my warning was worthless to you… I could do nothing to stop any of this… ~Tra-la-la~…"

"W-what are you talking about? Who is 'the man who speak in hands'?"

"He is the man out of time, out of space… most have forgotten him, but the few who remember are afraid… of what may happen when they find him again… That is the man who speaks in hands, who came from the other world…"

"… I-is this where I can f-find him?"

"You cannot find the man here, there, or anywhere… he will find YOU at the edge of nowhere… That is where you will meet the man who speaks in hands… ~Tra-la-la~…"

It seemed that the more answers Frisk would get, more questions arose. And yet, they would not be deterred.

"If I'm going to meet him, then can you at least tell me his name?"

"… I believe the answers you seek, remain behind that door…"

Frisk was confused until they turned around, seeing a large grey door appear against the wall of the corridor. It was plain and ordinary, yet had an ominous feeling to it, like it should not be here or anywhere. When Frisk turned back to the River Person, they found no-one there. Swallowing their fear, Frisk turned back to the door, walking towards it and putting their hand on the handle. Inside they went, only for the door to slam shut behind them.

The room they entered was something almost indescribable. Vast, yet narrow; harrowing, yet familiar. There was a distinct noise, and yet it conveys little beyond emptiness; like a low rumbling on a drill trying to get through a mile of titanium. However, there once one other thing Frisk could hear:

"_Dark… Darker… Yet Darker… The darkness keeps growing… The shadows cutting deeper… Photon readings: negative…"_

In the distance, Frisk could see a vaguely humanoid shape, a white oval shaped head on top of a black mass. Walking closer, they could make out the details of this figure much clearer. Chiefly, the head seemed to be that of a skeleton, bringing to mind their Dunkle and Brunkle. However, this skeleton seemed different from the Skelebros because of a pair of black cracks on the skull; one running from the top of the head down to the crescent shaped right eye, the other crack going from the bottom of the left eye down to the pointed chin. The only other detail sticking out from the black mass of body were a pair of bony hands with massive holes in the palms.

The skeleton seemed to not notice Frisk's presence, even when they were standing before each other.

"H-hello? Can y-you speak?"

Still no response. As a last tactic, they decided to reach out and grab the mysterious Monsters hand. As soon as they were close, however, one of the Monster's hands grasped their wrist, though not in a way that would cause Frisk harm. The voice returned.

"_This next experiment seems… Very… Very… Interesting…"_

The Monster's head slowly raised up, looking Frisk in the eye with a small white dot in the left eye. The mouth slowly curved into a small smile.

"_What do you think, human?"_

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I think that's enough for now. If you liked what you saw here, leave a review, follow and favourite.

I thought it was about time I followed up on that blink and you miss it reference to Gaster in my first Undertale fanfic, "A Second Chance". Same as that one, this may probably be at least 3 chapters long, possibly 5.

Sayonara, mother-lovers!


	2. Chapter 2

**DISCLAIMER:** I do not own Undertale.

A.N.: Not much in the way of traffic with this story, but I still want to get this one finished in about 3-4 more chapters. Not sure how it's going to go, I'm just kind of winging it (potential pun? Not really sure) at this point. Rest assured, however, that after this, I will be making a PTA fanfic. With that said, updates will be sporadic due to a bunch of real life stuff getting in the way.

Also, my headcanon voice for Gaster is Jeffrey Combs, better known as Ratchet from TF: Prime, Scarecrow from The New Batman Adventures, The Question from Justice League Unlimited and Dr Herbert West from the Re-Animator film series.

Hope you enjoy it; ON WITH THE SHOW!

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Frisk felt extremely uncomfortable with the Monster currently holding their wrist and staring them in the eye. What did not help matters was the Monster's eerie appearance and the overall surrounding; a gloomy, barren void that offered no comfort or sense of hope, yet also brought no malice or scorn. As the Monster kept looking at Frisk, the smile seemed to slope down slowly and a sense of realization glowed in his eyes, quickly letting go of the child's wrist.

"… _Forgive me, I had thought that you were… someone else…_"

Frisk's apprehension was replaced with a feeling of confusion. This Monster, from the way that he spoke, was clearly expecting a human, but not them specifically? Even with this confusion baring on their mind, the human could not help but bow to curiosity.

"… W-who are you? What is this place?"

"… _This place… I have come to call it the 'Void'. A realm that exists beyond time and space. An eternity could pass by outside of this place, and yet not a single second would even pass here. Only those who have made the greatest of mistakes end up here… never to leave again._"

Frisk could hear an ounce of regret seep into his voice as he turned his back to the child and sat down, head hanging low and shoulders slouching.

"_As for who I am… well, before I came here, I was the Royal Scientist for his majesty, King Asgore. Along with the other brilliant minds of the Underground, I had helped to create the Core to supply the Underground with power. It was a lot of hard work, but by God was it worth._"

Frisk came up next to the Monster, sitting down beside him as he told his story.

"… _But soon, we faced a great tragedy; losing the Crown Prince Asriel and their human sibling hit everyone hard. People became desperate to find some way to break the Barrier, if only to get some payback for the children. Once the Queen left, Asgore sought me out, begged me to find a way to destroy the Barrier, with or without the Souls he would eventually get. So, once the next human fell and their Soul was taken, I had a chance to study it; to understand the power it held to pass through the Barrier and persist after death. The power of—_"

"DETERMINATION."

The Monster looked at Frisk with a surprised face, but that surprise quickly faded once he realised what they had gone through in their original timeline.

"_Yes. Exactly that. Once I saw the near endless possibilities that one could use with DETERMINATION, I began examining what else it could do beyond persisting after the human had died. Through this, I theorised that if a human had enough DETERMINATION to keep going once their bodies were dust and ashes, they could also hold the power to change fate; manipulate the very fabric of reality itself and unlock the potential of time travel. Of course, your very existence proves that as fact, but this was long before you would fall._"

Frisk nodded, not fully grasping the larger details but still understanding the basics of what the Monster was trying to explain.

"What happened for you to end up here?"

The Monster seemed to shudder for a brief second. Whether it was out of dread or regret, Frisk could not decide.

"… _I built another machine that could be linked to the Core while also harvesting the DETERMINATION we had extracted from the first four human Souls we had collected at the time. With the machine powered by the Core to amplify the effects of DETERMINATION, I had hoped that the combined energy could allow all Monsters to access their SAVE files from before the Barrier was created. Thus, allowing everyone the chance to return to the Surface before the war began and preventing it from happening. We would be free. We would finally have peace with the humans._"

Frisk could already see what the result of the experiment could be but was still intrigued to hear the rest of the story.

"… _Unfortunately, it backfired. The Soul's levels of DETERMINATION were far too insufficient to power the machine properly, even all together. Instead of allowing us to access a specific SAVE file, it tore open a crack in the very fabric of reality itself. Inside the crack, there was only this place. I peered over to see what it could be, but there was a sudden quake and… I fell… before he had the chance to even grab me._"

"He? Who's he?"

"… _My son. The only one who never forgot about me, even when everyone else did… heh… even in spite of how lazy he often could be._"

Realization quickly dawned on Frisk, their mouth agape in surprise.

"Sans? You're his dad?"

"_I'm surprised you could not tell, given the resemblance. I would not think it HUMERUS to make that mistake._"

Suddenly, it made more sense for Frisk, as they let out a small giggle.

"Did you teach him that one?"

"_The opposite, actually. His wordplay always helped me get through my work, no matter how taxing the job or obvious the pun._"

"I guess it… tickled your _funny bone_?"

The Monster could not restrain himself from chortling.

"_My boy taught you well, human._"

"My name is—"

"_Frisk. Yes, I apologize. It would seem my time in this place has greatly affected my manners._"

"It's okay… What's your name?"

That seemed to put the Monster in a state of silence, the frown on his face now being more pronounced. Frisk quickly sensed how uncomfortable he became.

"I'm sorry. I didn't mean to—"

"_Gaster._"

Now it was Frisk's turn to be silenced.

"_My name; it's Dr W.D Gaster. But you may call me Gaster, if you so wish._"

"…Pleased to meet you, Dr Gaster."

"_The pleasure is mine, Frisk._"

The pair sat in a surprising comfortable silence, taking the opportunity to reflect on what had been shared between the pair in the last few minutes.

"Dr Gaster?"

"_Yes?_"

"If you were the Royal Scientist, did you ever know Alphys?"

"_KNOW her? She was an intern of mine, for a while. Quite the social butterfly, if I recall… at least, before she had her turn with the DETERMINATION experiments._"

"You know about those?"

"_I know about many things, Frisk. While I may not be able to physically interact with the timeline as I would have hoped to, I am aware of what several of my friends and loved ones could do. I can't explain it, but the Void seems to allow me to see various outcomes of ones actions. Sans', Asgores, Alphys'… Yours… I saw what she had done with her experiments. And I understood her pain. No one should have to go through that, especially one as kind as her._"

Suddenly, the atmosphere felt more uncomfortable than before, which was no shock given the subject matter. Still, Frisk didn't want this to be the running theme of their conversations.

"So… did Alphys ever show you any Anime?"

"_Oh, yes. Plenty, in fact. I can almost see it now; the excitement on her face when I had agreed to watch 'Mew Mew Kissy Cutie' with her, it was quite contagious. You know, were it not for her, I would not have found the majesty of 'Death Note' or 'Code Geass'. Now, if only 'MMKC 2' had anywhere near the creative talent of the first._"

"Trust me; I know. Alphys wanted me to see how bad it was, so invited me to watch it with her and Undyne when they moved in together."

"_Undyne? So my little friend finally found the courage to take a chance with her._"

"After a bit of encouragement, too. And some role-play."

"_Is that so? Oh, if only I had thought of such earlier. Still, I hope they are doing well?_"

"They're getting married in July!"

"_You don't say! That is simply wonderful news. When you return to them, I hope you tell them that I wish them a prosperous life together._"

"Why don't you tell them yourself?"

Gaster's joy suddenly vanished, his mouth left agape as he stared off into the distance.

"… _I can't._"

"Why not?"

"… _I have tried many a time to bring myself back to my own timeline. That door that the River Person showed you was the closest I had ever come with integrating myself back into reality. I am physically incapable of ever leaving this place… The Void seems to have a mind of its own, and it refuses to let me see my loved ones in person again. That is my curse, Frisk. I always know what everyone I cared for is doing, but I cannot intercede without risk of death._"

"… I am so sorry, Dr Gaster."

"… _It is no fault of your own, Frisk. This was years ago; long before you ever came._"

"… Wait; if you're trapped here—"

"_Don't worry; you came to this place willingly, so you can come and go as much you please without consequence. You can see your friends again._"

"… Does that mean I could bring someone else here if I wanted to?"

"_Yes. Why?_"

Seeing the plight that the good Dr was in, Frisk was filled with DETERMINATION.

"Because I think I can find a way to get you out of here!"

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That's enough for.

I hope you enjoyed what you saw and if you did, please follow and favourite, leave a review if you so choose. I appreciate any feedback I could get, be it a simple comment or constructive criticism. As always, no pressure, just thought I'd offer.

Good day to you, sir/madam/neutral!


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